package org.bouncycastle.jce.provider;

import java.math.BigInteger;
import java.security.InvalidKeyException;
import java.security.PrivateKey;
import java.security.SignatureException;
import java.security.SignatureSpi;
import java.security.spec.AlgorithmParameterSpec;

import org.bouncycastle.asn1.pkcs.PKCSObjectIdentifiers;
import org.bouncycastle.asn1.x509.X509ObjectIdentifiers;
import org.bouncycastle.crypto.DSA;
import org.bouncycastle.crypto.Digest;

public abstract class DSABase extends SignatureSpi implements
        PKCSObjectIdentifiers, X509ObjectIdentifiers {
    protected Digest digest;
    protected DSA signer;
    protected DSAEncoder encoder;

    protected DSABase(Digest digest, DSA signer, DSAEncoder encoder) {
        this.digest = digest;
        this.signer = signer;
        this.encoder = encoder;
    }

    protected void engineInitSign(PrivateKey privateKey)
            throws InvalidKeyException {
        engineInitSign(privateKey, null);
    }

    protected void engineUpdate(byte b) throws SignatureException {
        digest.update(b);
    }

    protected void engineUpdate(byte[] b, int off, int len)
            throws SignatureException {
        digest.update(b, off, len);
    }

    protected byte[] engineSign() throws SignatureException {
        byte[] hash = new byte[digest.getDigestSize()];

        digest.doFinal(hash, 0);

        try {
            BigInteger[] sig = signer.generateSignature(hash);

            return encoder.encode(sig[0], sig[1]);
        } catch (Exception e) {
            throw new SignatureException(e.toString());
        }
    }

    protected boolean engineVerify(byte[] sigBytes) throws SignatureException {
        byte[] hash = new byte[digest.getDigestSize()];

        digest.doFinal(hash, 0);

        BigInteger[] sig;

        try {
            sig = encoder.decode(sigBytes);
        } catch (Exception e) {
            throw new SignatureException("error decoding signature bytes.");
        }

        return signer.verifySignature(hash, sig[0], sig[1]);
    }

    protected void engineSetParameter(AlgorithmParameterSpec params) {
        throw new UnsupportedOperationException(
                "engineSetParameter unsupported");
    }

    /**
     * @deprecated replaced with <a href =
     *             "#engineSetParameter(java.security.spec.AlgorithmParameterSpec)"
     *             >
     */
    protected void engineSetParameter(String param, Object value) {
        throw new UnsupportedOperationException(
                "engineSetParameter unsupported");
    }

    /**
     * @deprecated
     */
    protected Object engineGetParameter(String param) {
        throw new UnsupportedOperationException(
                "engineSetParameter unsupported");
    }
}
